- Returns an iterator over - chunk_sizeelements of the slice at a
time.
 
- Returns an iterator over - chunk_sizeelements of the slice at a time.
 
- Creates parallel iterator if - parallelfeature is enabled.
 
- Creates parallel iterator over refs if - parallelfeature is enabled.
 
- Creates parallel iterator over mut refs if - parallelfeature is enabled.
 
- Applies the reduce operation over an iterator. 
- A macro for computing ceil(log2(x))+1 for a field element x. The num_bits
param is expected to be a vector to which the BE bits can be written; it is
not created here, as reusing it allows us to avoid a lot of allocations.